The present invention relates to improvements in machine controls and more particularly, to a mechanism for sensing obstructions in the tool path of machines used for welding, pressing, riveting and the like.
In spite of the increased complexity and trend toward automation of many machine processes, certain control devices are still required to reduce the danger to machine operators and to prevent damage to expensive machines from improper operation. While various types of devices are known, each generally employs a sensor which is introduced into a work area prior to the intitiation of machine tool movement. The movement of the sensor is intiated by the operator or by automatic control, but movement of the machine tool is conditioned upon the sensor not encountering any obstructions in the work area. In this manner, operator error and automatic controls cannot cause initiation of machine tool movement when obstructions may cause an unsafe condition in the work area.
In spite of the variety, prior art devices tend to be constructed for use in connection with a specific machine, thereby limiting their usefulness with many different machines. In addition, the devices have been constructed with numerous special parts and complex mechanical arrangements which increase the cost and repair time of each mechanism. As a result, their use decreases the efficiency of machine operation and encourages their bypass or elimination in order to continue machine operation. Since a primary concern is for operator safety, it is highly desirable to employ devices which will operate effectively for long periods of time as well as discourage and prohibit operation of a machine in an unsafe condition.
In one particular example shown by U.S. Pat. No. 3,487,182 to Grundy, a device is shown which employs a movable rod supporting a sensor which in turn moves coaxially along the path of machine tool movement. A plurality of guide blocks and special support configurations are used to position the sensor while additional elements are required to control the rate of gravity fall of the sensor into the work area. In addition, a special spring-yoke lever mechanism, directly connected to one end of the rod, is used to position and release the sensor. While the device appears to provide for effective sensing of obstructions and subsequent machine tool control, its complexity increases the likelihood of malfunction and decreases its versatility for use with a variety of machines.
Accordingly, the present invention has been developed to overcome the specific shortcomings of the above known and similar techniques, and to provide a less complex mechanism for controlling machine tool operation.